Liquid fuel burner



March 3, 1932. E AN 1,848,206

LIQUID FUEL BURNER Filed Oct. 3, 1930 I I s- .1

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' UNITED STATES PATENT OFFICE BALLSTON ll. SHERMAN, OF GLASTON'BUBY,CONNEGT IGU'T, 'ASSIGNOB TO THE SILENT GLOW OIL BURNER CORPORATION, OFHARTFORD, OONHEGI'IGUT, A GOBPORATION OF CONNECTICUT mom runn nvnnnn VApplication filed October 3, 1930. Serial ilo. 488,129.

This invention relates to oil burners of the type supplied with oil orother hydrocarbon fuel in liquid form, the fuel beingvaporized withinthe burner and there burned with a suitable mixture of air. Fordescriptive purposes the fuel herein referred to is oil, al though othertypes of liquid fuel may be employed.

A common type of such a burner is one pro? o vided with one or morecombustion chambers having perforated, tubular walls, through which airenters to mix with the oil vapor ascending from a fuel space, thelatterbeing usually in the form of a fuel groove, trough or other chamberbelow the combustion chamber, the mixture being burned in the combustionchamber and a blue flame issuing from the open upper end thereof,-

In starting a burner of this type from a cold condition, it is customarypreliminaril to heat the burner walls and base before fina ly turning onthe full continuing supply of oil. One common method of effecting suchpreliminary heating is. to provide the fuel groove or trough with anasbestos wick, which is first saturated with oil or other primingdeposits when present tend further to retard complete combustion,building up and clogging the fuel grooves and connecting ducts,interfering with the free flow of the oil in thin film-like form andtending to insulate the liquid oil from the heated walls of the burner.v This prolongs still further the starting interval, and these' depositsmust be removed from time to time with considerable inconvenience. Theirpresence on the bottoms and sides of the fuel grooves also provides amedium by which the oil, through capillary attraction; tends to creep upand over the sides of the grooves, with the resultant accumulation onthe outside of the 5 burner and its adjacent parts of oil, carbondeposits and dirt.

It has been the almost universal custom heretofore to construct thegrooved base of burners of this class fromcast metal, usually cast iron,in order to provide the necessary mass and rigidity to avoid burning outand warping. The fuel spaces which receive the liquid oil therebypresent oil contacting surfaces which are more or less rough, harsh andporous, with occasional blow holes either fluid and thenlighted by ataper. After a short interval, when the temperature of the adjoiningwalls of the burner is .sufiicient to cause vaporization of asubstantial portion of the oil reaching the fuel groove, the oil supplyis turned on. As the temperature rises the oil becomes vaporized at amore rapid rate, and after the lapse of a suitable interval, which maybe termed the starting interval, the oil reaching the fuel space orspaces is completely vaporized and an in tensely hot flame results.

These burners as heretofore constructed large or minute which areinevitable to the process of casting. The harshness and roughness ofthese surfaces become intensified through use due to the inevitableoxidization which takes place. This type of surface, due to the relativehigh surface tension of the oil thereon, tends to retard the free flowof oil and to cause it to enter the fuel space to which it is delivered,and to accumulate therein, in the form of a slow-flowing, relativelythick and more or less localized body as distinct from a thin,relatively tensionless film capable of spreading readily and rapidlyover the entire bottom of the fuel space or spaces to which it hasaccess, the latter condition representing the ideal condition for quick,

49 have had certain disadvantages. The time required for the startinginterval has been, quite substantial and prolonged, this being due inlarge part to the slow initial vaporization of the oil. This not onlyimposes a 4% measure of restriction on the use of such burners but tendsto produce incomplete combustion, particularly in the initial stages ofstarting, with the formation of deposits of unconsumed carbonon thewalls of the fuel space with which oil comes in contact. These rapidvaporization. The character of surface presented by the cast iron tendsto augment the deposits of unconsumed carbon, further prolonging thestarting interval, and to increase the difliculty with which thesedeposits are removed since they tend to cling tothe cast surface withgreat tenacity.

I have found that by so fashioning the burner as to provide a smooth,highly polished or glazed surface for the oil grooves, 01"

for those parts of the burner with which the oil tends to contact, thesurface tension of the oil is markedly reduced, it flows freely andunimpeded, quickly spreading over the entire available area in the formof a thin tensioiiless film. This results in accelerating itsvaporization, materially reducing the starting interval, retarding andcutting down the collection and deposits of unconsumed carbon andpreventing in large measure the seepage and filtration of oil over thesides of the grooves. Furthermore, such deposits of carbon which tend tocling tenaciously to the cast metal surfaces of the grooves and ductsare readily removed without difficulty from the smooth, polishedsurfaces of the grooves and ducts.-

In the preferred and illustrated embodiment of the invention, suchsurface is provided by coating the metallic oil contacting walls of thebase with some material such as vitreous enamel. Such coating-is capableof presenting a uniformly and permanently smooth, highly glazed surfaceincapable of oxidization, closing and covering the pores and blowholesin the base and permitting the oil to flow thereover under a relativelylow surface tension. The character of this surface thereby presented notonly speeds up the starting of the burner and assists in retarding theformation of deposits of unconsumed carbon,

but such effects are further enhanced by the coating itself. The lattertends to heat rapidly, while the external conduction of its heat to themetal of the base, due to the difference in character between-the twomaterials, is more or less retarded. The coated surface of the fuelgrooves therefore tends to heat morerapidly than the uncoated surfaceand more rapidly acquires the needed temperature for effectivelyvaporizing the oil. This also tends to prevent the casting itself fromoverheating, burning out or warping, and the casting as a consequencemay be made relatively less massive with a resultant reduction in theweight of the burner and the amount of metal required.

The invention will be best understood by reference to the followingdescription when taken in connection with the accompanying illustrationof one specific embodiment thereof while its scope will be moreparticularly pointed out in the appended claims.

In the drawings:

F'g. 1 is a plan oview of a burner embodying one form of the invention,the upper cover plates resting on 'the'tops of the sheet metal cylindersbeing partly broken away to better show the construction of, the basepart.

Fig. 2 is a vertical, central, sectional elevation, partly brokenaway,showing the burner illustrated in Fig. 1;

Fig. 3 is a sectional elevation on the line 3-3 in Fig. 1; and

Fig. 4 is an enlarged, sectional elevation in detail taken through theinner fuel space to show the application of the enamel coating to theinner surface thereof.

Referring to the drawings and to the embodiment of the invention whichis here submitted for illustrative purposes, the burner is provided witha base member 1 (Fig. 2) the body of which is of metal and herein ofcast iron. This comprises an outer annular plate 3 and an inner annularconcentric plate 5 connected one to the otherbyaseries of webs 7 (Figs.1 and 3), herein four in number, and providing for an annular airadmission space 9 between the plates, this space being interrupted onlyby the webs 7.

The inner plate 5 is provided with a central air admission opening 11surrounded by an upturned, ring-like flange 13, the outer edge of theinner plate having also an up.- turned, ring-like flange 15 spaced frombut concentriowith the flange 13.

The flanges 13 and 15, together with the bottom plate 5, form arelatively wide annular channel 17 presenting a fuel space or chamber,to the inner part of which the oil is delivered by a ,pipe' connection19 through an openin in the bottom of the channel. The top 0 the spacedefined by the channel is closed except for the direct escape ofvaporized fuel to the combustion chamber by a removable cover plate 21seated on the upper edge of the flange 13 and provided with a downwardlyextending rim or sleeve 23 which fits within the flange and positionsthe cover plate thereon. The walls of the plate 21 extendoutwardly andherein downwardly over the channel 17, being spaced vertically from thebottom of the channel and spaced peripherally from the inner walls ofthe flange 15 to provide an annular exit slot for the passage of thevaporized oil into the overhead combustion chamber.

The cover plate 21 is provided with an upturned, annular flange 25within which there is secured a perforated sheet metal cylinder 27. Asimilar but larger concentric cylinder 29 is removably seated on theouter shoulthroughout substantially theentire surface thereof, smallperforated areas only being shown in Fig. 2. It will also be understoodthat these perforations may be of any shape, size or arrangement so longas they provide suitable air admission openings for thecombustionchainber.

In the illustrated embodiment of the invention there is also provided anouter fuel space 33 formed between the upright, annular, spaced,concentric flanges 35 and 37 on the outer plate 3. Concentric, spaced,perforated sheet metal cylinders 39 and 41 are removably seated on theshouldered edges of the flanges 35 and 37, providing between them thecombustion chamber 43. The outer fuel space 33 is connected with theinner channel or fuel space 17 by means of the sup 1y ducts 45 (Figs. 1and 3) formed in the we s 7.

A removable cover plate 47 is provided with its edges resting on thetops of the sheet metal cylinders 39 and 41 to close the top of theannular air space therebetween, and a generally disc-shaped closureplate 49 with its edges resting on the upper edges of the cylinder 27 isslmilarly provided to close the top of the central air chamber, leavingannular openings at the top of the two combustion chambers 31 and 43 forthe escape of the products of combustion. The closure plates 47 and 49may, if desired, be provided with one or more apertures to permit thepartial escape of the air therethrough.

lVhile for simplicity a single burner unit only is shown, the sameconstructional features may be embodied in two or more duplicate units,the generally annular base member 1 being connected to the correspondingbase member of the other unit or units by webs integrally cast therewithor'by other connections.

The specifically described form of burner is shown merely asillustrative of one burner of a suitable type to which the presentinvention may be applied.-

In the operation of the burner, the latter is preliminarily heatedeither by igniting an asbestos wick (not herein shown) positioned inthefuel space and saturated with oil admitted through the supply pipe23, or by means of a priming fluid alone placed in the fuel spaces, orin any other desired manner. After the burner has been preliminarilyheated,-liquid fuel is then admitted through the fuel supply pipe 19under the regulation of any of the usual feeding devices. These commonlyprovide for the flow of fuel from a feeding device at some definitelevel which may be accurately regulated so thatthe flow of fuel may bemaintalned at an approximately predetermined level over the flowsurf-aces which are presented by the channels or grooves 17 and 33 and aflow thereby maintained of rel tively shallow depth, spreading over theflow surfaces in a more or less film-. like form. Such regulatingdevices are of the usual or common construction and are not hereinshown.

In the initial starting stage of the burner this oil film becomesvaporized by the heat imparted thereto from the surfaces of the fuelspaces with which it contacts, this vaporiz'ation at firstproceedingslowly and taking area of the uel s bout the entire oil contacting acesbut accelerating more or less ra idly, ependent to a substantial extenton t e freedom with which the oil flows over the surfaces, the thinnessof the film of oil, and the rapidity with which the oil contactingsurfaces acquire and store up the necessary heat for vaporization. Afterthe starting period, andwhen the burner is in full effective operation,vaporization will take place almost wholly in the vaporizing space whichis formed by the broad covered inner place throu part of the channel 17,the bottom of which provides a flow surface of considerable area for theentering oil, and the oil will passin vaporized form into the outer partof the fuel space 17 which registers with and opens into the innercombustion chamber 31 and through the ducts 45 to the outer fuel space33 and thence into the outer combustion chamber 43.

In order to impart to the oil contacting walls of the fuel space thedesired character of flow surfaces already explained, the base casting 1is prepared by applying a baked vitreous enamel coating 51 to the flowsurfaces, such a coating being represented in the drawings herein byheavy black lines of exaggerated thickness to distinguish them fromother heavy shade lines. In the described embodiment this coating isapplied not only to the bottom of each fuel space 17 and 33 (Figs. 2 and4) ,but to the sides thereof as well as to the inner walls of the duct45 (Fig. 3), thereby providing a smooth, glazed, enamel surface coveringall parts of the base with which the liquid oil can come in contact inthe normal operation of the burner both during the starting interval andthereafter.

Any of the usual or well-known processes for enameling cast ironarticles may be employed fo'r'this purpose. By way of example only, thefollowing enameling rocess mag be utilized. A composition is rst formeconsisting of 12 parts of potters clay, 8 parts of borax, 10 parts ofWhitelead, 2 parts of potassium nitrate, 1 part of calcined whitemarble, 2 parts of purified potash and 5 arts of calx of tin. Thiscomposition is nely powdered, mixed and fused. When cold, the

resultant vitreous mass is ground to a powder, sifted and mixed withwater toform a thin paste. J The casting is cleaned, as by pickling, andthen dried. The paste is then applied to the surfaces of the ase castingwhich are to becoated by dipping, brushing or spraying. The sides andbottoms of the fuel spaces 17 and 33 and the walls of the ducts 45having been coated with the paste, the base casting is then placed in abanking or enameling oven and subjected to a sufficiently hightemperature to fuse the coating, after which it is allowed to cool.

The described construction provides a burner functioning. in adistinctly improved manner in that the oil supplied during startingvaporizes at a more rapid rate the starting interval is materiallyreduce and deosits of unconsumed carbon are retarded. ihe surface isuniformly and permanently smooth, impervious to the effects of oxid ze.-tion through continued usage and provides for an extremely low surfacetension for the oil. The surface coating being of enamel heatsup rapidlyand yields its heat to the thin oil film thereon, conduction of the heatto the base casting being more or less retarded. While I have hereinshown for the pur ose of illustration one specific embodiment o theinvention as applied to one specific t pe or form of burner, it is to beunderstood t at the coating surface may be produced in various wa s andthat it may be applied to widely different forms of burners, all withoutdeparting from the spirit of the invention.

Claims:

1. A burner having sets of spaced, con centric tubular, perforated Wallsto rovlde between them a plurality of com ustion chambers, a cast metalbase member having a plurality of fuel grooves communicating one witheach of said chambers, supply ducts connecting said grooves, and meansfor supplying liquid fuel to one of said grooves, the surfaces in saidgrooves and ducts which are adapted to contact with the liquid fuelsupply being covered with a glazed coating of vitreous enamel.

2. A burner having spaced, perforated, tubular walls one enclosing theother to provide between them a combustion chamber, a cast metal basemember havin a fuel chamber communicating with said combustion chamber,in which fuel chamber the vaporization of liquid fuel is adapted to takeplace during operation of the burner, and means fortsupplying liquidfuel to said fuel chamber, the said fuel chamber having its surfaceswhichare adapted to contact with the liquid fuel supply covered with aglazed coating of vitreous enamel.

8. A burner having spaced, perforated, tubular walls one enclosing theother to provide between them a combustion chamber, a cast metal basemember having a fuel chamber communicating with said combustion chamber,in which fuel chamber the vaporization of liquid fuel is adapted to takeplace during operation of the burner, and means for supplying liquidfuel to said fuel chamber, the said-fuel chamber having its surfaceswhich are adapted to contact with the liquid fuel supply covered with acoating presenting a smooth, polished surface.

4. A burner having a combustion chamber, a communicating fuel chamber inwhich the vaporization of liquid fuel is adapted to take place duringoperation of the burner, and means for supplying liquid fuel to saidfuel chamber, the said fuel chamber having its surfaces which areadapted to contact with the liquid fuel supply covered with a coatingpresenting a smooth, polished surface.

5. A burner having a combustion chamber, a communicating fuel chamber inwhich the vaporization of liquid hydrocarbon fuel is ada ted to takeplace during the operation of the urner, and means for supplying li uidhydrocarbon to said chamber, the said uel chamber presenting surfaceswhich are adapted to contact with the liquid fuel supply and presentinga smooth, polished surface adagted to provide a low surface tension to te liquid fuel contacting therewith.

6. Aliquid fuel burner having a base, a lperforate tubular wallsupported on said ase and forming a combustion chamber thereover, andmeans for supplying liquid fuel to said base, said burner havingsurfaces in its said base covered with a glazed coating of vitreousenamel to receive and vaporize sald liquid fuel.

7; Fuel receiving and vaporizing means for liquid fuelburners comprisinga metallic member provided with a fuel vaporizing surface having aglazed coating of vitreous enamel adapted to receive liquid fuel andvaporize the same thereon.

8. A burner having a base provided with a vaporizing surface, aperforated tubular wall supported on said base and forming a combustionchamber thereover arranged to receive vapor from said vaporizingsurface, and means for supplying liquid fuel to said vaporizing surface,said vaporizing surface comprising a coating presenting a smooth,polished surface.

In testimony whereof, I have signed my name to this s ecification.

RA LSTON M. SHERMAN.

